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Headgasket for 35-40psi??

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camfast

10+ Year Contributor
432
23
Jun 6, 2008
Houston, Texas
I just got my cylinder head redone from the machine shop and I also have ARP head studs. Which headgasket would work best if i want to eventually run 30-40 psi?? I was thinking a Mitsu mls headgasket?? Any suggestion is appreciated. thanks
 
You do not want to sand the head with just your hand. Use A peice of machined steel bar stock that is 2"x2"x12" with one side machined perfectly flat. This has worked quite well for me for many heads. This is something that a lot of other high power guys have done before as well, because some machine shops cant get the surface finish needed to seal a MLS gasket at extremely high cylinder pressures, like those generated when you are putting out between 700 - 1100 hp.

From my experience, the smoother the better with MLS.

ok, is it necessary for the surface to be real smooth if im planning on 450-500rwhp?
 
ok, is it necessary for the surface to be real smooth if im planning on 450-500rwhp?

Needing it to be smooth has nothing to do with horsepower ratings, its about MATING the surfaces for a seal on a MLS headgasket. It should be done with any MLS headgasket.
 
I'll vouch for 30 psi with stock head gasket and head bolts, it really does come down to the tuner and if he/she knows what they are doing. Also who ever it was is exactly correct, NEVER hand sand a head/block or any surface for that matter. Second, throw a little copper head gasket spray down, that always helps, third if you are going to run over 30 psi the head SHOULD be o-ringed, fourth, how does one know that crush carachteristics of over torquing the head using the L91s, fith NEVER NEVER use a crapmetic head gasket... garbage :notgood:, the FEL PRO MLS gasket is the only way to go, a hair exspensive but worth ever penny summit usually stocks them.

Later Dr Turbo
 
The standard machine shop finish on the mating surfaces will not be smooth enough most of the time. Have you done the fingernail test? Can you see the cutting marks?

So, do you need to take the parts to a special machine shop for the work to be done? All I have is standard machine shops around me.
 
So im confused, I have heard 4 different types of logic:
1) Use the Felpro HG and L19's, call it a day!
2) The stock HG and head studs are good for 30psi, with a 'smart' tune.
3) Standard ARP's are proven for 8-9 second passes.
4) The block should be o ringed if over 30psi????

I personally will be running a HTA 30r to 30-33 psi(or where ever it runs out of steam) and im gonna run a fel pro with standard ARP's. I think o ring'ing the block is overkill for most applications.

Lets get a consensus agreement on what HG and studs to use with:
0-30 psi
31-35 psi
36+ Psi
 
Why are you set on 40psi? Unless your looking for 800+ hp there is really no need to go that high. You also have a lot more to worry about than just a headgasket and some studs.
Hx40 at 40psi....hmm. What does that turbo flow like 50-55lb/min? You will be past that if you have a good setup IMO.
I'm flowing 46-48lb/min on 22-23psi.
Either way, 30psi should be MORE than enough for the average person, hell 24psi is more than enough for most people.
I have a cometic headgasket and arp studs, I plan on doing 35psi this summer (if I can afford other stuff, like bigger injectors etc) just to see what it feels like, but I know it will be wayy too much for a street car.

That is my .02, take it or leave it.
 
Why are you set on 40psi? Unless your looking for 800+ hp there is really no need to go that high. You also have a lot more to worry about than just a headgasket and some studs.
Hx40 at 40psi....hmm. What does that turbo flow like 50-55lb/min? You will be past that if you have a good setup IMO.
I'm flowing 46-48lb/min on 22-23psi.
Either way, 30psi should be MORE than enough for the average person, hell 24psi is more than enough for most people.
I have a cometic headgasket and arp studs, I plan on doing 35psi this summer (if I can afford other stuff, like bigger injectors etc) just to see what it feels like, but I know it will be wayy too much for a street car.

That is my .02, take it or leave it.

I couldnt imagine less that 25psi for a street car...LOL

My car survived a couple years of 30+psi runs on pump gas and race gas using a cometic hg and standard arp studs. I have since switched to a mitsu mls and arp l19's
 
So, do you need to take the parts to a special machine shop for the work to be done? All I have is standard machine shops around me.

Most shops should be able to handle it. Find one that has done a few 4g63`s. If you don`t let them know what you need, you`ll probably get a surface suitable for the standard composite gasket.

I run 37lbs of boost with a 150 shot in my race car. The Felpro/A1 combonation holds for me. The Cometic/standard ARP combo has failed under the same conditions.

I think your crazy to run this kind of boost on the street. Maybe I`m just old.
 
Why are you set on 40psi? Unless your looking for 800+ hp there is really no need to go that high. You also have a lot more to worry about than just a headgasket and some studs.
Hx40 at 40psi....hmm. What does that turbo flow like 50-55lb/min? You will be past that if you have a good setup IMO.
I'm flowing 46-48lb/min on 22-23psi.
Either way, 30psi should be MORE than enough for the average person, hell 24psi is more than enough for most people.
I have a cometic headgasket and arp studs, I plan on doing 35psi this summer (if I can afford other stuff, like bigger injectors etc) just to see what it feels like, but I know it will be wayy too much for a street car.

That is my .02, take it or leave it.

Im not really set on 40psi but i was just throwing a high boost number. True, 40psi would be overkill as i would break other components but down the road it may be very well possible. 30psi is more of what im planning to run on E-85 and can be achieved on a variety of turbos. Also my talon is not a daily driver but more of a fun track car too.

My cylinder head got some work done by a reputable machine shop but now im confused because as stated by others not all shops have the capability to get a perfect finish. To me it seems like it is very well done and the mating surface is smooth. As of now i have 12mm arp headstuds and it has the felpro MLS headgsket. With that being said I will get a new gasket (felpro mls) since its done well and then go from there.
 
Most shops should be able to handle it. Find one that has done a few 4g63`s. If you don`t let them know what you need, you`ll probably get a surface suitable for the standard composite gasket.

I run 37lbs of boost with a 150 shot in my race car. The Felpro/A1 combonation holds for me. The Cometic/standard ARP combo has failed under the same conditions.

I think your crazy to run this kind of boost on the street. Maybe I`m just old.

I know, I was being sarcastic.
 
I was wondering why a "wiseman" would be asking that question. I dable in the art a sarcasm myself.
 
O-ringed block with copper o-rings, mitsu MLS headgasket and standard ARP's have worked very well for me on my street car. I am running 41psi on E85 with a GT4094.
 
So im confused, I have heard 4 different types of logic:
1) Use the Felpro HG and L19's, call it a day!
2) The stock HG and head studs are good for 30psi, with a 'smart' tune.
3) Standard ARP's are proven for 8-9 second passes.
4) The block should be o ringed if over 30psi????

I personally will be running a HTA 30r to 30-33 psi(or where ever it runs out of steam) and im gonna run a fel pro with standard ARP's. I think o ring'ing the block is overkill for most applications.

Lets get a consensus agreement on what HG and studs to use with:
0-30 psi
31-35 psi
36+ Psi

0-30 the stock stuff is adequate, most people however when pulling a head go ahead and buy head studs from arp because the bolts do strech and should only be used once or twice, you can measure the strech if you want, just from experience twice is about it.

Really anything over 30 psi the head needs to be oringed it just seals better as that amount of boost want to blow out the fire ring in the head gasket, the oringing process just supports the head gasket better.

The multi layer steel is pretty straight foward, the steel is stonger than the composite material so the fire ring will hold up better just as if oringing because it is supported by that steel instead of weak composite, but composites seal oil and coolant better because of that huge squish area, that is why it is important to spray metal head gaskets. However this shouldn't be a problem if you are getting both block and head milled, but most of the time a head swap is done that is not the case. Any gasket should be sprayed really, weather it be a paper TB gasket or head gasket. There are many different types of adhesive sprays from permatex, choose which ones you should use for each application.

Now at the really high amounts of boost like 40 psi the head will litterally start to lift so that baby needs those L91s which are 1/2" compared to 12mm stock, they are stronger and dont stretch as much, so those are needed to keep the head from lifting.

The most important thing is of course the tune, I don't care if you weld the head to the block, detonation destroys everything, so make sure the car is tuned correctly. I bought a dsm once were there was a channel from #3 to a coolant passage, looked like a worm burroughed its way through/across the head, guy said it had wastegate failure and ran a bazillion psi. I threw a new head on it, and ran 28-30 for two years daily driving with used stock head bolts and a composite gasket.

Let me condense:

0-30 use stock shit factory head gasket approx $50
30-40 arps with mitsu mls gasket pretty cheap good combo approx $200
40+ L91s with Fel Pro MLS, big bucks, but big boost, so pay the piper. approx $450

Later Dr Turbo
 
Most shops should be able to handle it. Find one that has done a few 4g63`s. If you don`t let them know what you need, you`ll probably get a surface suitable for the standard composite gasket.

I run 37lbs of boost with a 150 shot in my race car. The Felpro/A1 combonation holds for me. The Cometic/standard ARP combo has failed under the same conditions.

I think your crazy to run this kind of boost on the street. Maybe I`m just old.

Hey u2slow,

What do you think was caused the failure with the Cometic/standard arp setup?


Thanks,
Kag

**Edit**

I just read HighBooost post and with what he said I think I would use arp bolts and a MLS gasket. what would be the best MLS gasket out there for its price?

sorry for hijacking the thread op.
 
I'll vouch for 30 psi with stock head gasket and head bolts, it really does come down to the tuner and if he/she knows what they are doing. Also who ever it was is exactly correct, NEVER hand sand a head/block or any surface for that matter. Second, throw a little copper head gasket spray down, that always helps, third if you are going to run over 30 psi the head SHOULD be o-ringed, fourth, how does one know that crush carachteristics of over torquing the head using the L91s, fith NEVER NEVER use a crapmetic head gasket... garbage :notgood:, the FEL PRO MLS gasket is the only way to go, a hair exspensive but worth ever penny summit usually stocks them.

Later Dr Turbo


from much experience with mustangs, when running really high boost, o-rings was the only option.
 
kanagader-I`m glad you asked that question. When I re-read my own post it sounded like I`m blaming Cometic/ARP. The conditions weren`t really the same. It was most likely the block/head preparation. I could see cutting marks in the block when I took it apart. I was and am still learning.

I learned that the "big boys" were using fel-pro/A1 and had a talk with my machinist about preparation. There`s not been a head gasket problem since.

I can say that the fel-pro/A1 combo works. I can`t really say the Cometic/ARP won`t work, because of the block preparation.
 
kanagader-I`m glad you asked that question. When I re-read my own post it sounded like I`m blaming Cometic/ARP. The conditions weren`t really the same. It was most likely the block/head preparation. I could see cutting marks in the block when I took it apart. I was and am still learning.

I learned that the "big boys" were using fel-pro/A1 and had a talk with my machinist about preparation. There`s not been a head gasket problem since.

I can say that the fel-pro/A1 combo works. I can`t really say the Cometic/ARP won`t work, because of the block preparation.

Good thing you had a talk with your machinist about the preparations. even with the best stuff it all comes down to how well it was prep and prepared.

I'm leaning towards buying mitsu MLS with Arp standard since what I'm building is going to be my daily fun car (think that setup can hold 25-30psi from a BW S258 good?)
 
Now at the really high amounts of boost like 40 psi the head will litterally start to lift so that baby needs those L91s which are 1/2" compared to 12mm stock, they are stronger and dont stretch as much, so those are needed to keep the head from lifting.


Later Dr Turbo

They are L19's, not L91's. And L19's are 12mm just like the standard stock size, not 1/2". If they were 1/2", I would have had to drill and tap my block to accept them and I would have also had to ream the bolt holes in the head for it to fit over the 1/2" studs. I didnt have to do any of this. It was a straight forward swap from arp standards to L19's.
 
so keith if i wanted to run let say 25-35 psi for the drag strip and the street would you say
the mitsu 4layer with l19's is over kill?? :hmm:

i feel copper spray wouldn't be a good idea to spray on the hg because when the head heats up it needs to expand a lil and the copper spray wouldn't allow that to happen.. which could cause premature failure?? or at least thats what i was taught in school??
 
so keith if i wanted to run let say 25-35 psi for the drag strip and the street would you say
the mitsu 4layer with l19's is over kill?? :hmm:

i feel copper spray wouldn't be a good idea to spray on the hg because when the head heats up it needs to expand a lil and the copper spray wouldn't allow that to happen.. which could cause premature failure?? or at least thats what i was taught in school??

What turbo will you be running? Mine did fine with standard arp studs and a cometic hg at 35psi with the 60-1. Also worked well street driven at 28psi on 93 pump gas. I only went to the L19's because of what the future holds, which you already know about. ;)

And honestly, I have never used a metal hg without using copper spray. Even my 2g rs has copper spray on the hg, which Doug99rs advised highly against. I think that engine has over 50k on it now without the slightest issues.
 
They are L19's, not L91's. And L19's are 12mm just like the standard stock size, not 1/2". If they were 1/2", I would have had to drill and tap my block to accept them and I would have also had to ream the bolt holes in the head for it to fit over the 1/2" studs. I didnt have to do any of this. It was a straight forward swap from arp standards to L19's.

My bad it is the A1s where the body and nut is 1/2" the threads are still 12mm.

Later Dr Turbo
 
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